1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device and a substrate processing apparatus.
More particularly, the present invention relates to a method for forming a high-quality interface between a wafer and a thin film in a process for forming a thin film on a semiconductor wafer (hereinafter, referred to as a wafer) in a fabrication method of an integrated circuit (hereinafter, referred to as IC) including a semiconductor device, and a substrate processing apparatus for realizing the forming method.
2. Description of the Prior Art
In the IC fabrication method, a thin film is formed on a wafer by a low pressure chemical vapor deposition (LP-CVD) method.
In recent years, when a wafer is introduced into a reactor, the following method has been used for solving problems such as semiconductor degradation caused by increase of a natural oxide film or impurity attachment.
A preparatory chamber is installed at a front stage of the reactor. After oxygen or moisture is sufficiently removed from the preparatory chamber and the inside of the preparatory chamber is replaced with a nitrogen gas, a wafer is introduced into the reactor.
The LP-CVD method is performed by using a vertical-type LP-CVD apparatus (hereinafter, referred to as a CVD apparatus having a preparatory chamber) which is installed in a vacuum-exhaustible sealing mechanism at a front stage of the reactor.
In the CVD apparatus having the preparatory chamber, an unprocessed wafer is loaded from a wafer transfer opening into the preparatory chamber and then set in a boat, a wafer processing jig. Thereafter, the preparatory chamber is air-tightly closed, and oxygen or moisture is removed by repeating the vacuum exhaust and the nitrogen purge. Then, the wafer is loaded from the preparatory chamber into the reactor by the boat.
However, in the CVD apparatus having the preparatory chamber, a wafer surface may be contaminated during the vacuum exhaust by contaminants such as organic materials, because a driving shaft or a boat rotating mechanism and a pipeline for loading the wafer and the boat into the reactor are installed inside the preparatory chamber.
Therefore, a hydrogen (H2) annealing method has been used for removing a natural oxide film or impurity from the wafer by using a reaction gas within the reactor where the wafer is loaded. For example, see Patent Document 1.
[Patent Document 1] Japanese Patent Publication No. H5-29309
However, since the hydrogen annealing method generally requires a high temperature process of 900-1000° C., there will arise a problem that increases a thermal damage and a thermal budget of IC.
Herein, when forming a high-quality interface between a wafer and a thin film at a low oxygen and carbon dose, it is important to suppress contamination of the surface of the wafer, which is introduced into the CVD apparatus having the preparatory chamber, to the minimum until a film is formed in the reactor.
Specifically, it is necessary to seek a cleaning method of a wafer surface as follows.
During the nitrogen replacement before the loading of the wafer into the reactor and during the unloading of the wafer from the reactor, the preparatory chamber suppresses the contamination of the wafer surface with organic materials from the driving shaft, the boat rotating mechanism and the wirings.
The inside of the reactor suppresses the contamination from a relatively low-temperature furnace throat and a wafer itself.
The cleaning of the atmosphere inside the reactor, and the reduction and release of contaminants adsorbed on the wafer surface are performed before a thin film is formed on the wafer.
When the wafer surface is to be cleaned in batch, for example, in a mass-production process for processing 100-150 wafers, by using the CVD apparatus having the preparatory chamber, the contamination of the wafer surface may be generated unevenly in a wafer interfacial direction inside the reactor, that is, a wafer arrangement direction, due to degassing from the relatively low-temperature furnace throat or the wafer.